KR20110026331A - Apparatus and method for control ammonia occlusion amount of selective catalytic reduction system - Google Patents

Abstract

PURPOSE: An apparatus and a method for controlling the ammonia occlusion amount of a selective catalytic reduction system are provided to enable the spraying of urea solution to be accurately controlled to generate ammonia since ammonia consumption is accurately predicted on the SCR(selective catalytic reduction) system. CONSTITUTION: An apparatus for controlling the ammonia occlusion amount of a selective catalytic reduction system comprises a SCR catalyst, first and second temperature sensors, an NOx sensor and a controller. The occluded ammonia reacts with NOx by the SCR catalyst to purify the NOx. The first and second temperature sensors detect the temperatures of the front and rear ends of the SCR catalyst. The NOx sensor detects the amount of NOx, which flows into the SCR catalyst. The controller calculates total ammonia required for the SCR catalyst and controls occlusion.

Description

Apparatus and method for controlling the amount of ammonia occlusion of SCR catalyst {APPARATUS AND METHOD FOR CONTROL AMMONIA OCCLUSION AMOUNT OF SELECTIVE CATALYTIC REDUCTION SYSTEM}

The present invention relates to an SCR (Selective Catalytic Reduction) catalyst mounted on a diesel vehicle, and more particularly, to ammonia storage amount control apparatus and method for controlling the amount of ammonia in consideration of the axial temperature difference of the SCR catalyst. It is about.

Diesel-powered vehicles can be used in various forms to remove hazardous substances such as NOx, CO, THC, and Particulate Matters contained in the exhaust according to the North American diesel Tier 2 / BIN 5 regulation or the Euro 6 emission regulation. The aftertreatment device is mounted.

As a post-treatment device, the DOC (Diesel Oxidation Catalyst), which collects non-methane hydrocarbons (NMHC), and the Particulate Particulate Filter (DPF), which collect particulate matter (PM), which reduce NMHC, SCR catalyst is included to purify NOx.

The SCR catalyst uses ammonia (NH ₃ ) as a reducing agent for purifying NOx, and has an advantage that the reaction between NOx and ammonia is promoted even in the presence of oxygen as well as excellent selectivity to NOx. have.

SCR catalyst sprays urea into a dosing module placed at the front end of the SCR catalyst to maintain NOx purification performance at a certain level or higher, and ammonia generated by evaporation and decomposition of the injected urea And ammonia is occluded inside the SCR catalyst, and the ammonia occlusion amount is inversely proportional to the SCR catalyst temperature.

In the conventional vehicle, it is assumed that there is no difference in the temperature inside the SCR catalyst, the front and rear temperatures of the SCR catalyst are detected, averaged, and extracted as the temperature of the SCR catalyst, and the temperature value is applied to the set map to the volume of the SCR catalyst. The target amount of ammonia occlusion was determined by predicting the possible amount of ammonia occlusion.

The required amount of ammonia was determined according to the difference between the target ammonia occlusion amount and the current ammonia occlusion amount of the SCR catalyst.

The adsorption amount of ammonia in the SCR catalyst is slower when the temperature of the SCR catalyst is low and the adsorption amount is large because the adsorption amount is large. The difference in quantity proceeds in small form.

As such, if there is a temperature difference in the SCR catalyst, there is a difference in the amount of possible ammonia occlusion in the axial direction. Let's do it.

For example, the purification of the NOx is stable at the front end of the SCR catalyst, but there is a problem that the NOx slip occurs due to the purification loss of the NOx at the rear end.

The present invention has been made to solve the above problems, and its object is to improve the NOx purification rate by providing a uniform ammonia distribution in the SCR catalyst by performing ammonia storage amount control considering the axial temperature difference of the SCR catalyst, A more accurate injection of the element does not cause ammonia slip to provide emission stabilization.

Ammonia storage amount control apparatus of the SCR catalyst according to the characteristics of the present invention for achieving the above object,

SCR catalyst for purifying NOx by reacting the ammonia occluded with NOx;

First and second temperature sensors for detecting temperatures before and after the SCR catalyst;

NOx sensor for detecting the amount of NOx flowing into the SCR catalyst;

According to the front and rear temperature of the SCR catalyst, the inside of the SCR catalyst is divided into N blocks that maintain the temperature difference, and the required amount of ammonia for each block is calculated by applying an axial response model module to each block, and calculated for each block. And a control unit for controlling the amount of occlusion by calculating the required amount of ammonia of the entire SCR catalyst by summing up the required amount of ammonia.

In addition, the ammonia storage amount control method of the SCR catalyst according to the characteristics of the present invention,

Collecting general information from sensors before and after the SCR catalyst;

Dividing the inside of the SCR catalyst into N blocks having a temperature difference according to the temperature before and after the SCR catalyst;

Calculating a required amount of ammonia for each block by applying an axial response model module to each of the divided blocks;

Calculating the required amount of ammonia for the entire SCR catalyst by summing the required amount of ammonia calculated for each block and controlling the amount of occlusion.

By the above-described configuration, the present invention provides a uniform distribution of ammonia in the SCR catalyst to maximize the NOx purification rate and exclude ammonia slip to stabilize the emission.

In addition, the response of NOx purification is improved in response to rapid changes in exhaust conditions, and the prediction of ammonia consumption on the SCR catalyst is enhanced to provide precise injection control of aqueous urea solution to generate ammonia, and to prevent excessive or underproduction of ammonia. Keep your emissions stable.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Since the present invention can be implemented in various different forms, the present invention is not limited to the exemplary embodiments described herein, and parts not related to the description are omitted in the drawings in order to clearly describe the present invention.

1 is a view schematically showing an apparatus for controlling ammonia storage amount of an SCR catalyst according to an embodiment of the present invention.

The present invention is an engine (2) as a power source, an exhaust pipe (6) for discharging exhaust gas burned by the engine (2), an SCR catalyst (10), a first NOx sensor (12), a second NOx sensor (14), a first Temperature sensor 16, second temperature sensor 18, dosing module 20, mixer 22, urea tank 30, pump 32, urea supply line 34, pressure sensor 36 and control unit And 40.

The SCR catalyst 10 is made of V ₂ O ₅ / TiO ₂ or Pt / Al ₂ O ₃ or zeolite, and is disposed at a predetermined position of the exhaust pipe 6 connected to the engine 2 as a power source. The NOx is purified by reducing the ammonia and NOx absorbed from the urea injected from the dosing module 20 and NOx.

The first NOx sensor 12 is disposed in front of the dosing module 20 to detect the amount of NOx contained in the exhaust gas flowing into the SCR catalyst 10 and provide the information to the controller 40.

The second NOx sensor 14 is disposed at the rear end (outlet side) of the SCR catalyst 10 to detect the amount of NOx contained in the exhaust gas purified through the SCR catalyst 10 and provide the information to the controller 40. .

The first temperature sensor 16 is disposed in front of the SCR catalyst 10 to detect the front temperature of the SCR catalyst 10 and provide the information to the controller 40.

The second temperature sensor 18 is disposed at the rear end of the SCR catalyst 10 to detect the rear temperature of the SCR catalyst 10 and provide the information to the controller 40.

The dosing module 20 operates the injector under the control of the control unit 40 to inject the urea amount for generating ammonia for occlusion in the SCR catalyst 10.

Mixer 22 is disposed between the dosing module 20 and the SCR catalyst 10 to collide the liquid element particles injected through the dosing module 20 to split the particles, thereby the exhaust gas and the injected elements The particles are evenly mixed to improve uniformity at the inlet end of the SCR catalyst 10 so as to optimally mix NOx in the exhaust gas and ammonia obtained from urea.

The urea tank 30 receives the urea solution and forms an even pressure set in the urea supply line 34 by driving the pump 32 mounted therein, so that the SCR catalyst 10 when the dosing module 20 is operated. High pressure injection of the liquid element is provided at the front end of the

The pressure sensor 36 detects the pressure formed in the urea supply line 34 and provides information about the pressure to the control unit 40 so that the set pressure can be maintained at all times while the engine 2 is kept starting. Make sure

The controller 40 applies an axial temperature model to the front / rear end temperatures of the SCR catalyst 10 detected by the first and second temperature sensors 16 and 18 to adjust different temperatures inside the SCR catalyst 10. It is divided into N blocks (for example, 5 to 10), and the required amount of ammonia is calculated for each block through the axial response model module.

The calculation of the amount of ammonia required for each block applies the temperature of each block (T.SCR) to the ammonia storage capacity map per volume, and applies the actual volume for each block divided therein to calculate the ammonia storage capacity for each block according to the temperature difference. Calculate

Also, the actual ammonia storage amount is calculated from the amount of ammonia (NH3.In), NOx amount (NOx.In), and NOx purification rate input to the SCR catalyst 10, and the difference between the ammonia storage capacity and the actual ammonia storage amount is calculated. Calculate the amount of ammonia needed.

Then, the required amount of ammonia calculated for each block is added to calculate the required amount of ammonia for occlusion in the entire SCR catalyst 10.

When the amount of ammonia required for occlusion in the SCR catalyst 10 is calculated as described above, the amount of urea injection is controlled through the dosing module 20.

In the present invention including the function described above, the operation of controlling the amount of ammonia occlusion of the SCR catalyst is as follows.

When the engine of the diesel vehicle to which the present invention is applied is started, the controller 40 collects general information necessary for controlling the amount of ammonia occlusion through various sensors installed at front and rear ends of the SCR catalyst 10 (S110).

For example, the front temperature T. In of the SCR catalyst 10 is detected from the first temperature sensor 16, and the rear temperature T. Out of the SCR catalyst 10 is detected from the second temperature sensor 18. Detects and extracts the ammonia injection amount (NH3 injection amount) generated by the urea aqueous solution injected from the dosing module 20, and the amount of NOx (NOx.In) flowing into the SCR catalyst 10 from the first NOx sensor 12 Detect.

Subsequently, by applying the axial temperature model set to the temperature of the front and rear of the SCR catalyst 10 detected from the first and second temperature sensors 16 and 18 (S120), the temperature difference in the SCR catalyst 10 is reduced. It is divided into N blocks (T.1 to T.5) having (S130).

As described above, when the SCR catalyst 10 is divided into N blocks through the temperature model, the axial reaction model module is applied to each block (S140), and the required amount of ammonia is calculated for each block (S150).

As shown in FIG. 3, the calculation of the amount of ammonia required for each block is performed by applying the temperature (T.SCR) for each block to the ammonia storage capacity map per volume to extract the ammonia storage capacity per volume (S151), By applying the actual volume for each block to calculate the amount of ammonia occlusion for each block according to the temperature difference (S152).

In addition, the actual ammonia storage amount is calculated from the amount of ammonia (NH3.In), NOx amount (NOx.In) and NOx purification rate input to the SCR catalyst 10 (S153), The required amount of ammonia is calculated from the difference in the actual amount of ammonia occlusion calculated in S153.

As described above, when the required ammonia amount is calculated for each block in which a plurality of SCR catalysts 10 are separated according to the difference in temperature, the required ammonia required in the entire SCR catalyst 10 is added by adding up the required amount of ammonia in each block. Calculate the amount (S160).

When the required amount of ammonia required in the entire SCR catalyst 10 is calculated as described above, the amount of ammonia stored in the axial direction of the SCR catalyst 10 is controlled by controlling the amount of urea injection through the dosing module 20, as shown in FIG. It is maintained in a uniform distribution to stabilize the emission by increasing the purification rate of NOx.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It is included in the scope of rights.

1 is a view schematically showing an ammonia storage amount control apparatus of the SCR catalyst according to an embodiment of the present invention.

2 is a flowchart illustrating a procedure for controlling ammonia storage amount of the SCR catalyst according to the embodiment of the present invention.

3 is a flowchart illustrating a detailed procedure of the axial response model module in FIG.

4 is a graph showing the ammonia storage amount control results of the SCR catalyst according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

2: engine 6: exhaust pipe

10: SCR catalyst 12: 1st NOx sensor

14 second NOx sensor 16 first temperature sensor

18: second temperature sensor 20: dosing module

22: mixer 30: urea tank

40: control unit

Claims (7)

SCR catalyst for purifying NOx by reacting the ammonia occluded with NOx; First and second temperature sensors for detecting temperatures before and after the SCR catalyst; NOx sensor for detecting the amount of NOx flowing into the SCR catalyst; The inside of the SCR catalyst is divided into N blocks having different temperatures according to the front and rear temperatures of the SCR catalyst, and the required amount of ammonia for each block is calculated by applying an axial reaction model module to each divided block, A control unit for controlling the amount of occlusion by calculating the required amount of ammonia for the entire SCR catalyst by summing the amount of ammonia calculated for each star; Ammonia storage amount control device of the SCR catalyst comprising a. The method of claim 1, The control unit calculates the ammonia occlusion amount according to the actual volume of each block by applying the temperature of each block to the set map, calculates the actual ammonia occlusion amount from the ammonia amount, NOx amount and NOx purification rate input to the SCR catalyst, An apparatus for controlling ammonia occlusion amount of an SCR catalyst, comprising calculating the amount of ammonia required per block from the difference between the ammonia occlusion amount and the actual ammonia occlusion amount. The method of claim 1, The controller divides the ammonia storage amount of the SCR catalyst into N blocks having different temperatures by applying an axial temperature model set to the front / rear temperature of the SCR catalyst detected by the first and second temperature sensors. Control unit. Collecting general information from sensors before and after the SCR catalyst; Dividing the inside of the SCR catalyst into N blocks maintaining a temperature difference according to the temperature before and after the SCR catalyst; Calculating a required amount of ammonia for each block by applying an axial response model module to each of the divided blocks; Controlling the occlusion amount by calculating the required amount of ammonia of the entire SCR catalyst by summing the required amount of ammonia calculated for each block; Ammonia storage amount control method of the SCR catalyst comprising a. The method of claim 4, wherein Block division of the SCR catalyst is, A method for controlling the amount of ammonia occlusion of an SCR catalyst, characterized by dividing into N blocks in which a temperature difference is maintained by applying an axial temperature model set to the front / rear temperature of the SCR catalyst. The method of claim 4, wherein The calculation of the amount of ammonia required per block, Calculating the amount of ammonia occlusion according to the actual volume of each block by applying the temperature of each block to the set map; Calculating the actual amount of ammonia occlusion from the amount of ammonia, NOx amount and NOx purification rate input to the SCR catalyst; Calculating a necessary amount of ammonia for each block from the difference between the amount of ammonia storage possible for each block and the actual amount of ammonia storage for each block; Ammonia storage amount control method of the SCR catalyst comprising a. The method of claim 4, wherein The information collected from the sensors before and after the CR catalyst, A method for controlling the amount of ammonia occlusion of an SCR catalyst, comprising the amount of ammonia generated from urea and input into the SCR catalyst, the amount of NOx contained in the exhaust gas, and the temperature before and after the SCR catalyst.

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